// SPDX-License-Identifier: GPL-2.0-only
/*
 * ledtrig-cpu.c - LED trigger based on CPU activity
 *
 * This LED trigger will be registered for first 8 CPUs and named
 * as cpu0..cpu7. There's additional trigger called cpu that
 * is on when any CPU is active.
 *
 * If you want support for arbitrary number of CPUs, make it one trigger,
 * with additional sysfs file selecting which CPU to watch.
 *
 * It can be bound to any LED just like other triggers using either a
 * board file or via sysfs interface.
 *
 * An API named ledtrig_cpu is exported for any user, who want to add CPU
 * activity indication in their code.
 *
 * Copyright 2011 Linus Walleij <linus.walleij@linaro.org>
 * Copyright 2011 - 2012 Bryan Wu <bryan.wu@canonical.com>
 */

#include <linux/kernel.h>
#include <linux/init.h>
#include <linux/slab.h>
#include <linux/percpu.h>
#include <linux/syscore_ops.h>
#include <linux/rwsem.h>
#include <linux/cpu.h>
#include "../leds.h"

#define MAX_NAME_LEN    8

struct led_trigger_cpu {
        bool is_active;
        char name[MAX_NAME_LEN];
        struct led_trigger *_trig;
};

static DEFINE_PER_CPU(struct led_trigger_cpu, cpu_trig);

static struct led_trigger *trig_cpu_all;
static atomic_t num_active_cpus = ATOMIC_INIT(0);

/**
 * ledtrig_cpu - emit a CPU event as a trigger
 * @ledevt: CPU event to be emitted
 *
 * Emit a CPU event on a CPU core, which will trigger a
 * bound LED to turn on or turn off.
 */
void ledtrig_cpu(enum cpu_led_event ledevt)
{
        struct led_trigger_cpu *trig = this_cpu_ptr(&cpu_trig);
        bool is_active = trig->is_active;

        /* Locate the correct CPU LED */
        switch (ledevt) {
        case CPU_LED_IDLE_END:
        case CPU_LED_START:
                /* Will turn the LED on, max brightness */
                is_active = true;
                break;

        case CPU_LED_IDLE_START:
        case CPU_LED_STOP:
        case CPU_LED_HALTED:
                /* Will turn the LED off */
                is_active = false;
                break;

        default:
                /* Will leave the LED as it is */
                break;
        }

        if (is_active != trig->is_active) {
                unsigned int active_cpus;
                unsigned int total_cpus;

                /* Update trigger state */
                trig->is_active = is_active;
                atomic_add(is_active ? 1 : -1, &num_active_cpus);
                active_cpus = atomic_read(&num_active_cpus);
                total_cpus = num_present_cpus();

                led_trigger_event(trig->_trig,
                        is_active ? LED_FULL : LED_OFF);


                led_trigger_event(trig_cpu_all,
                        DIV_ROUND_UP(LED_FULL * active_cpus, total_cpus));

        }
}
EXPORT_SYMBOL(ledtrig_cpu);

static int ledtrig_cpu_syscore_suspend(void *data)
{
        ledtrig_cpu(CPU_LED_STOP);
        return 0;
}

static void ledtrig_cpu_syscore_resume(void *data)
{
        ledtrig_cpu(CPU_LED_START);
}

static void ledtrig_cpu_syscore_shutdown(void *data)
{
        ledtrig_cpu(CPU_LED_HALTED);
}

static const struct syscore_ops ledtrig_cpu_syscore_ops = {
        .shutdown       = ledtrig_cpu_syscore_shutdown,
        .suspend        = ledtrig_cpu_syscore_suspend,
        .resume         = ledtrig_cpu_syscore_resume,
};

static struct syscore ledtrig_cpu_syscore = {
        .ops = &ledtrig_cpu_syscore_ops,
};

static int ledtrig_online_cpu(unsigned int cpu)
{
        ledtrig_cpu(CPU_LED_START);
        return 0;
}

static int ledtrig_prepare_down_cpu(unsigned int cpu)
{
        ledtrig_cpu(CPU_LED_STOP);
        return 0;
}

static int __init ledtrig_cpu_init(void)
{
        unsigned int cpu;
        int ret;

        /* Supports up to 9999 cpu cores */
        BUILD_BUG_ON(CONFIG_NR_CPUS > 9999);

        /*
         * Registering a trigger for all CPUs.
         */
        led_trigger_register_simple("cpu", &trig_cpu_all);

        /*
         * Registering CPU led trigger for each CPU core here
         * ignores CPU hotplug, but after this CPU hotplug works
         * fine with this trigger.
         */
        for_each_possible_cpu(cpu) {
                struct led_trigger_cpu *trig = &per_cpu(cpu_trig, cpu);

                if (cpu >= 8)
                        continue;

                snprintf(trig->name, MAX_NAME_LEN, "cpu%u", cpu);

                led_trigger_register_simple(trig->name, &trig->_trig);
        }

        register_syscore(&ledtrig_cpu_syscore);

        ret = cpuhp_setup_state(CPUHP_AP_ONLINE_DYN, "leds/trigger:starting",
                                ledtrig_online_cpu, ledtrig_prepare_down_cpu);
        if (ret < 0)
                pr_err("CPU hotplug notifier for ledtrig-cpu could not be registered: %d\n",
                       ret);

        pr_info("ledtrig-cpu: registered to indicate activity on CPUs\n");

        return 0;
}
device_initcall(ledtrig_cpu_init);